In the packaging industry, improved techniques for sealing products into containers are continually being sought. The product can be almost anything which will fit into containers, such as screws, fasteners, or food products. Oftentimes, a membrane or flexible seal is affixed to the product container, forming a seal which protects the product or retains the product within the container. When it is desired to use the product, the flexible seal must be removed by the consumer. The force required to remove the seal is important. If too much force is required, the consumer will have great difficulty opening the product container, leading to consumer dissatisfaction. On the other hand, the seal must be secured with sufficient strength so that the product is held within the container and, in the case of food product, protected from spoilage.
The flexible seal is typically attached to the container by packaging equipment. The strength of the bond between the seal and the container is determined by adjustments which are performed on the packaging equipment. For instance, the amount and type of adhesive applied to a seal are factors affecting the strength of the seal-container bond. If the bond is formed by means of heat, the amount and distribution of applied thermal energy will govern the strength of the bond.
During initial set-up of the packaging equipment, it is desirable to test the force required to remove the seal from the container so that the proper seal removal forces can be achieved. Periodic testing is also desirable so that the packaging equipment can be adjusted for operation within specified parameters. Thus, there is a need for an accurate way of measuring seal removal forces.
Apparatus for measuring seal removal forces is known in the art. One prior arrangement, disclosed in Kimura et al., U.S. Pat. No. 4,893,503 measures the force required to remove a seal from a container along a line parallel to the surface of the seal. The force measured parallel to the seal surface does not, however, accurately represent the force required at the angle of seal removal most often used by consumers. Consumer removal forces are more accurately measured at an angle of approximately 45.degree. with respect to the seal surface.
Another prior arrangement disclosed in U.S. Pat. No. 4,958,521, issued to Morimoto et al., measures forces required to remove a flexible seal from a tape-like product at an angle simulating consumer removal. The Morimoto et al. arrangement, however, requires complex mechanisms, such as precisely configured bevel gears which move both the product and the flexible seal in order to achieve a consistent removal angle. The complexity of such apparatus increases its expense, and renders maintenance and operation relatively difficult.
Flexible seals are often employed in the food preparation industry to affix a removable seal over a cup containing a liquid or semi-liquid food product. Handling such liquids in a packaging environment is somewhat more complex than handling solid products. Prior force measuring devices often employ mechanical clamps for retaining the container being tested. These clamps, if used with a liquid product, may provide adequate retention for seal removal, but in practice, the container is often punctured, or the product is often spilled, resulting in time-consuming cleanup of the apparatus.
A need exists in the art for a device which measures the removal forces of flexible seals at an angle simulating consumer removal, while avoiding the complexity of prior arrangements. A need also exists for apparatus which holds containers while seal removal forces are being measured in such a manner that product spillage or leakage is avoided.